Collaborative Research: Design of a Novel Photo-Thermo-Catalyst for Enhanced Activity and Stability of Dry Reforming of Methane
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Waste gases containing methane (CH4) and carbon dioxide (CO2) are produced from sources such as shale oil recovery, landfills, poultry and livestock farms, and other biogas sources. One way to upgrade those gases is to react them in the presence of catalysts to transform them into simple gases such as carbon monoxide (CO) and hydrogen (H2) that can be further processed to a wide range of chemicals and fuels. The catalyzed reaction between methane and carbon dioxide requires extremely high temperatures which makes it unattractive from an energy consumption standpoint. An alternative approach is to utilize a combination of direct sunlight irradiation and heat generated via solar energy collectors to react the gases via simultaneous photocatalysis and thermal catalysis in a sustainable process driven solely by the sun''s energy. The project explores that concept using a novel approach known as thermo-photo-catalytic dry reforming of methane (DRM). Specifically, the project will focus on catalyst designs that combine direct photocatalysis with thermal catalysis to achieve stable, highly-efficient DRM at temperatures much lower than those based on conventional fossil-fuel thermal catalysis alone. The technology can potentially play a significant role in sustainably meeting our nation''s future energy needs while simultaneously transforming the greenhouse gases - CH4 and CO2 - to useful fuels and chemicals.The project will investigate several novel aspects of thermo-photo-catalytic DRM, including: (1) fabricating novel and stable catalysts that promote synergy between the photo- and thermo-catalytic effects via integration of a photocatalytically active support, inexpensive metal nanocatalysts dispersed on the support, and promoters to enhance catalytic activity and stability; (2) designing innovative nanostructures, i.e. an ultrathin porous overcoat on the catalyst via atomic layer deposition (ALD) to mitigate metal sintering and prevent coke formation; (3) understanding the fundamental mechanism of photo-thermo-catalysis at elevated temperatures through a combination of in situ DRIFTS (diffuse reflectance FTIR) spectroscopy, GC/MS measurement of the catalyst activity, and experiments using isotopically labeled CO2 and CH4 molecules; and (4) elucidating catalyst structure-activity-stability relationships through operando studies of metal valence, nanoparticle size, and overcoat pore structure changes, carried out utilizing in situ X-ray scattering, X-ray diffraction, and X-ray absorption spectroscopy at the Advanced Photon Source of Argonne National Laboratory. This research will advance fundamental understanding in the interdisciplinary areas of heterogeneous catalysis, surface chemistry, nanoscience, and spectroscopy. In addition to the technical component of the research, the project will be supported by several programs at both institutions aimed at providing both high-school students and their teachers opportunities to develop research skills.This award reflects NSF''s statutory mission and has been deemed worthy of support through evaluation using the Foundation''s intellectual merit and broader impacts review criteria.